Reversing gear drive for a telemetric receiver



N 1966 w. H. FRAZEL 3,285,086

REVERSING GEAR DRIVE FOR A TELEMETRIC RECEIVER Filed 001:. 9, 1963 5 Sheets-Sheet 1 Nov. 15, 1966 w. H. FRAZEL 3,285,086

REVERSING GEAR DRIVE FOR A TELEMETRIC RECEIVER Filed Oct. 9, 1965 :3 Sheets-Sheet 2 F'|G.4. FIGG.

Nov. 15, 1966 w. H. FRAZEL. 3,285,086

REVERSING GEAR DRIVE FOR A TELEMETRIC RECEIVER Filed Oct. 9, 1963 3 Sheets-Sheet 3 United States Patent 3,285,086 REVERSING GEAR DRIVE FOR A TELEMETRIC RECEIVER Wilbur H. Frazel, East Providence, R.I., assignor to The New York Air Brake Company, New York, N.Y., a

corporation of New Jersey Filed Oct. 9, 1963, Ser. No. 315,063 6 Claims. (Cl. 74319) This invention relates to telemetering and, more particularly, to an improved receiver for use in a telemetering system.

In US. Patent 2,976,740 there is shown and described a telemetering receiver for use in impulse-duration type of telemetering systems. Such a system employs a transmitter having a cam continuously rotatable at substantially constant speed which, with cooperating contact means, sends in each of successive cycles of rotation of the cam an electrical impulse of a duration corresponding to a variable magnitude, such as, rate of flow, temperature, or pressure. The electrical impulses are fed to a receiver. In the receiver of the aforementioned patent, these electrical impulses, through an arrangement of gears and clutches are translated into a visual reading.

While the receiver of the patent is satisfactory for many installations, where excessive amounts of oil and/ or water vapors are present in the atmosphere or if the receiver is inadvertently overlubricated, slippage may occur in the clutch mechanism, possibly resulting in erratic action and inaccuracies in the visual reading.

It ,is an object of this invention to provide an improved telemetering receiver.

A further object is to provide a compact and lightweight receiver in which the impulses are transmitted through a locking drive.

A still further object is to provide such a receiver in which the received impulses are transmitted to the visual translator without slippage.

These and other objects will be apparent from the following description and the accompanying drawings in which:

FIG. 1 is a top plan view of the device of the instant invention;

FIG. 2 is a front View of the device of FIG. 1;

FIG. 3 is a side view of the device of FIG. 1;

FIG. 4 is a view along the line 4-4 of FIG. 1;

FIG. 5 is an enlarged view, partly in section, along the line 55 of FIG. 1, and in addition, showing diagrammatically, the telemetering circuit and transmitter;

FIG. 6 is a view along the line 66 of FIG. 1;

FIG. 7 is a view along the line 77 of FIG. 1; and

FIG. 8 is an enlarged view illustrating the interlocking driving surfaces.

Referring to the drawings illustrating a preferred embodiment, the invention is shown in connection with a telemetric receiver, connected to an electrical circuit which includes a transmitter of any suitable or well-known type. As shown in FIG. 5, the transmitter includes a motor 2 which rotates at substantially constant speed to drive a cam 4. Motor 2 is connected by leads 6, 8 to a suitable power source, not shown. A contactor 10, engageable by the cam 4 during each cycle of rotation of the cam, is

carried by a rod 12 supported for vertical movement between pairs of rollers 14. Rod 12 is vertically positioned between rollers 14, by mechanism not shown, in accordance with the instantaneous magnitude of the variable being measured, for example, pressure, temperature or fluid flow. Thus, the relative position of contactor to cam 4 is regulated by the variable being measured. Current is fed to cam 4 through lead 16. During a portion of each cycle of rotation, cam 4 closes a circuit ICC through contactor 10 for a time duration proportional to the instantaneous magnitude of the variable being measured. For the balance of such rotation, contactor 10 is out ,of engagement with cam 4 and the circuit is open.

Referring particularly to FIGS. 1, 3 and 5, the receiver includes spaced frames 18, 20, 22 positioned in fixed spaced positions by screws 24, 26, 28 and spacers 30, 32,

. 34 and 36, 38, 40. A shaft 42 is mounted for axial movement in frames 20, 22 and is in axial alignment with shaft 44 mounted in fixed axial position for rotation in frames 18, 20. A clearance is provided between the abutting ends of shafts 42, 44 to allow axial movement of the former toward and away from the latter. Intermediate frames 20, 22, driving plates 46, 48 are mounted on suitable bearings 66, 70 for rotation concentric with the axis of shaft 42. At their periphery, plates 46, 48 are provided with rings 50, 52, respectively. Rings 50, 52 are fixed to their respective plates for rotation therewith. For reasons more apparent hereinafter, rings 50, 52 are preferably fabricated from self-lubricating material, such as nylon, and are provided around their respective peripheries with gear teeth 54, 56. Radially inward from teeth 54, 56, the facing sides of rings 50, 52 are provided with stepped teeth 58, 60.

A U-shaped spring 62 is positioned between plates 46, 48 and urges the plates in opposite directions toward frames 20, 22. Plate 46 is provided with a thrust bearing 64 for engagement with a thrust bearing insert 66 carried in a recess in frame 20. Similarly, plate 48 is provided with a thrust bearing 68 for engagement with a thrust bearing insert 70 carried in a recess in frame 22. A plate 72 fixed to shaft 42 for axial movement therewith is mounted intermediate plates 46, 48. Near its periphery, plate 72 freely engages spacer 36, the spacer preventing rotation but not axial movement of the plate and shaft (FIG. 7).

An arm 74 is rotatably mounted on shaft 42 intermediate plates 46, 72, the outer end of arm 74 being bent upon itself to form a U-shaped end. Near its outer U-shaped end, arm 74 is provided with a collar 76, the collar having stepped teeth 78, the stepped teeth 78 being positioned on arm 74 for engagement with stepped teeth 58 on ring 50. Collar 76 is preferably fabricated from a self-lubricating material, such as nylon. At its opposite end, arm 74 is provided with a spacer collar 80, which keeps the arm 74 substantially parallel to plate 46 when the arm 74 is urged toward plate 46 to engage teeth 78 with teeth 58. A spiral spring 82 is attached at one of its ends to plate 72 and, at its opposite end, to arm 74, spring 82 urging arm 74 toward spacer 36 which acts as a stop for the arm.

A second arm 84 is rotatably mounted on shaft 42 intermediate plates 48, 72, the outer end of arm 84 being bent upon itself to form a 'U-shaped end for contact with a stop 85 mounted for adjustment in spacer 38 (FIG. 7). Near its outer U-shaped end, arm 84 is provided with a collar 86, the collar having stepped teeth 88, the stepped teeth and collar being positioned on arm 84 for engagement with the stepped teeth 60 on ring 52. Like collar 76, collar 86, with its stepped teeth 88, is preferably fabricated from a self lubricating material, such as nylon. At its opposite end, arm 84 is provided with a spacer collar 90, for the same purpose as already described in connection with spacer collar 80. Collars 76, 86 are each provided with a pin 91, 93, pin 91 having a head 95 and pin 93, a head 97. As best shown in FIGS. 5 and 7, each pin extends outwardly from its respective collar and through a relieved portion 99 along the outer edge of plate 72, the heads 95, 97 being on opposite sides of plate 72, each on the side of the plate opposite that of its respective collar. A spiral spring 92 is attached, at one of its ends, to plate 72, and at its opposite end, to arm 84, spring 92 urging arm 84 toward spacer 38 and into engagement with adjustable stop 85.

An L-shaped arm 89 is keyed at one of its ends to shaft 44 and, at its opposite end, extends over frame 20 and between the outwardly extending ends of arms 74, 84. Arm 89 is provided with stops 89a and 89b positioned between rings 50, 52, the stops being normally out of contact with the rings but positioned to contact the rings and maintain the rings spaced should spring 62 be inadequate to hold the desired spacing .at the instant of tooth disengagement. A gear 94 is keyed to shaft 44 at one side of arm 89, and shaft 44 is provided with a spring 96 which, at its outer ends, bears on a plate 98 carried in frame 20. Spring 96 urges arm 89 and gear 94 toward frame 18 and, with the frame, acts as a brake to hold the gear and arm in position for reasons more apparent hereinafter.

A solenoid 98 is mounted on the back of frame 22. Solenoid 98 is provided with an armature 100 hinged, at one of its ends, to the stationary frame of the solenoid. At its opposite end, armature 100 engages nut 104 adjustably mounted on shaft 42. Intermediate nut 104 and frame 22, shaft 42 is provided with a shoulder 106. A ring 108 is carried on shaft 42 and is slidable on the shaft between shoulder 106 and the inner side of armature 100. A coil compression spring 110 is seated, at one of its ends, on frame 22 and, at its opposite end, on one side of ring 108. A second coil compression spring 112 is seated, at one of its ends, on the opposite side of ring 108 and, at its opposite end, an armature 100. It is preferred, for reasons more apparent hereinafter, that the compressive foroeof spring 112 be twice the force of spring 110.

A motor 114 is mounted on the back of frame 22 and drives a gear 116 at constant speed. Motor 114 is connected to power leads 6, 8. Gear 116 is in driving mesh with teeth 56 of ring 52 carried on plate 48 and is also meshed with gear 118 keyed to counter-shaft 1 20 rotatably mounted, at its opposite ends, on plates 20, 22. Gear 122 is also keyed to shaft 120, gear 122 being meshed for driving engagement with gear teeth 54 of ring 50 fixed to plate 46. As motor 114 rotates gear 116 at substantially constant speed, due to the intermes'hing gears, plates 46, 48 are rotated at equal and constant angular speeds but in opposite directions.

Referring now to FIG. 8, the stepped teeth 58, 78 on ring 50 and collar 76, respectively, are shown in enlarged detail. In the following description, it is to be understood that the configuration of the stepped teeth 60, 88 on ring 52 and collar 86, are identical.

Referring still to FIG. 8, ring 50 is rotated in the direction of the arrow. Each of the teeth 58 has a surface A extending substantially normal to the direction of movement of the ring, and an angularly disposed surface B extending angularly with respect to the surface A, and the direction of movement of the ring. The teeth 78 on collar 76 have a surface C extending substantially normal to the direction of movement of the collar and an angularly disposed surface D.

As best shown in FIGS. 1, 2 and 4, a gear segment 130 is keyed to a shaft 132 supported for rotation on frames 18, 20, with the teeth of gear segment 130 in mesh with the teeth of gear 94. Shaft 132 extends through frame 18 and, on the outer side of the frame, is provided with a pionter 134 fixed to the shaft. At its outer end, pointer 134 sweeps a scale 136.

. In operation, motor 114 is connected through leads 6, 8 to a power source and drives plates 46, 48 and their :respective rings 50, 52 .at substantially constant speeds solenoid 98 open, springs 110, 112 urge armature 1% away from the solenoid and shaft 42 is in its outermost position, that is, at the position shown in FIG. 5.

With shaft 42 in its outermost position, plate 72 fixed to shaft 42 is positioned toward plate 48 and arm 84, the stepped teeth 88 of collar 86 carried by arm 84 are in engagement with stepped teeth 60 on ring 52 carried on plate 48. With plate 72 positioned toward arm 84 and plate 48, head 97 of pin 93 is engaged by plate 72 holding arm 74 away from plate 46 and ring 50.

As viewed from the front of the receiver, motor 114 drives plate 48 and ring 52 in a counterclockwise direction and plate 46 and ring 50 in a clockwise direction. Thus, when solenoid 98 is d e-energized and stepped teeth 88 are in engagement with stepped teeth 60, arm 84 is rotated in a counterclockwise direction concentric with the axis of shaft 42. As arm 84 rotates in a counterclockwise direction around shaft 42, the U-shaped end of the arm, when it contacts arm 89, moves arm 89 and gear 94 in a counterclockwise direction, gear 94, through gear segment 130 moving pointer 134 with respect to scale 136.

When solenoid 98 is energized, armature is attracted to the core and shaft 42 is moved into the housing against the action of springs 110, 112. As solenoid 98 attracts armature 100, plate 72 fixed to shaft 42 is moved away from plate 48 and toward plate 46. In moving away from plate 48, plate 72 engages head 95 of pin 91 and disengages the stepped teeth 60, 88 of ring 52 and collar 86, respectively. At the same time, in moving toward plate 46, head 97 of pin 93 is disengaged by plate 72, the center hub of plate 72 engages the center hub of arm 74 and stepped teeth 78 on collar 76 engage stepped teeth 58 on ring 50.

Plate 46 and ring 50 are rotated by motor 114 in a clockwise direction with respect to shaft 42 when viewed from the front of the receiver. With teeth 78, 58 in engagement, arm 74 is rotated concentric with the axis of shaft 42 in a clockwise direction, the outer U-shaped end of arm 74, when it contacts arm 89, moves arm 89 and gear 94 in a clockwise direction and, through gear segment 130, moves pointer 134 with respect to scale 136. When solenoid 98 is again dc-energized, armature 180 is again released, springs 110, 112 move shaft 42 outward of the housing and plate 72 away from plate 46 and toward plate 48. Stepped teeth 78, 58 are dis-engaged and teeth 88, 60 re-engaged.

As can be readily seen from the foregoing, rotation of plates 46, 48 selectively rotate arms 74, 84 depending upon the position of plate 72 under the control of solenoid 98. As arms 74, 84 rotate, the outer U-shaped end of the arms are moved through an arc, the length of such are depending on the time interval during which solenoid 98 is energized or de-energized. so long as the time interval remains constant, each of the arms 74, 84 is brought up to arm 89, released and returned by its coil spring (82 or 92) to its initial starting point. As the one arm is released and returned to its starting point, the other arm is engaged and starts driving. While the time interval remains constant, arm 89, gear 94, gear section and pointer 134 are held in fixed position by spring 96.

When the time interval during which solenoid 98 is energized or de-energized is changed, the arcs through which arms 74, 84 are driven likewise change. Thus, in the case where solenoid 98 is energized for a longer time interval and de-energized for a shorter time interval, arm 74 will be driven through a longer are and arm 84 a shorter arc. During the first cycle after time interval change, arms 74, 84, as the case may be, moving through the longer are will contact and reposition arm 89 and pointer 134. Arm 89 and pointer 134 will again remain in fixed position until the next change in time interval.

When stepped teeth 78, 88 of collars 76, 86 are brought into engagement with stepped teeth 58, 60, respectively, it

is, of course, possible that the teeth on the driven arms may not be in exact alignment with the teeth on the driving plates. For example, in FIG. 8 the teeth are shown slightly misaligned and when arm 74 carrying collar 76 is moved toward ring 50 carried by driving plate 46, a slight relative movement occurs before ring 5!) drives collar 76. Because of the configuration of the gear teeth, when misalignment occurs, the movement of collar 78 and its arm 74 is momentarily delayed. Hence, the arc through which the driven arm is rotated is slightly less than the intended full are. This loss in arc travel is, of course, at its maximum when the stepped teeth of the driven collar and the driving ring are brought into engagement with the vertical face of the teeth on the driven collar just behind the vertical face of the teeth on the driving ring, and is at its minimum when the stepped teeth on the driven collar and on the driving ring are brought into engagement with the vertical faces of the teeth in exact alignment.

Loss of arc travel, of course, affects the accuracy of the receiver. Where the loss is at its maximum the length of the arc is decreased just short of a full tooth length. While some loss is tolerable the loss is substantially reduced in the receiver of instant invention by special selection of the number of stepped teeth on the rings 76, 86 of driving plates 46, 48 so that a fraction of a tooth is included in the number of teeth contained in the angular movement of rings 76, 86 corresponding to one complete cycle of the transmitter cam. For example, assume that the driving plates 46, 48 rotate through an arc of exactly 90 during the time of one complete cycle of rotation of the transmitter cam, and that the stepped teeth 58, 68 of rings 56, 52 carried by plates 46, 48 are so spaced that, within such 90, there are 250% teeth. In this arrangement, and assuming that on the first cycle the stepped teeth of the driven collar and the driving ring are brought into engagement with the vertical faces of the teeth on the driven collar just behind the vertical faces of the teeth on the driving ring, the loss in arc travel will be at its maximum and just short of a full tooth length. During the first cycle the driving plate will advance 250 whole teeth plus tooth. Also, during the cycle the driven arm is disengaged from the driving plate and is returned by its spring to its initial position. When the stepped teeth are re-engaged at the beginning of the next cycle the driven arm will be tooth less out of alignment. Hence, on the second cycle the loss in arc travel will be just short of of a tooth length. At the beginning of the third cycle the teeth will be only just short of /2 tooth out of alignment and just short of /2 of a tooth length will be lost in arc travel. On re-engagment of the teeth in the fourth cycle the teeth Will be only just short of tooth length out of alignment. On the fifth cycle the teeth on the driven arm and driving plate will be in the same alignment as on the first cycle. Thus by this arrangement four operating cycles reduce the arc loss to less than A of a tooth length. Once the magnitude of the variable being measured at the transmitter changes, a visual indication of the changed magnitude of the variable will be reflected at the visual indicator on the receiver to an accuracy of A of a tooth length by the time the receiver has completed four cycles. Assuming a gear on the driving plate with 1001 teeth and having a driving arc of 90, the tooth loss is well within the intended accuracy of such a receiver. Obviously, by varying the extra tooth fraction and the number of cycles, the accuracy may be changed. For example, if the fractional tooth in the driving are is one-tenth of a tooth, within ten cycles the visual indication would be accurate to less than one-tenth of a tooth length.

Although the teeth carried by the driving plates and the teeth on the driven arms are of a self-lubricating material, it is possible that the relative movement of the teeth, during engagement and disengagement may cause wear. Thus, it is desirable in the receiver of the instant invention to avoid closely repeated re-engagement of particular teeth. By utilizing an odd number of teeth on one of the gears in the spur gear train of motor 114, engagement between the teeth on the rings of the driving plate and the teeth on the driven collars is shifted every four cycles. This permits a more even distribution of any wear which may occur.

As shown in FIG. 5, receiver motor 114 and transmitter motor 2 may be connected in parallel through leads 6, 8 to a single power source, not shown. Motors 114 and 2 must be constant speed motors, preferably synchronous, with output speeds selected so that the time lapse of one complete revolution of transmitter cam 4 is equal to the elapsed time required to drive either arm 74 or 84 through the full are between 36, 38 eliminating from such full arc, of course, the width of arm 89 and the set adjustment of stop 85. Stated in another way, the time lapse of one complete revolution of transmitter cam 4 is equal to the total elapsed time required to drive arm 74 from spacer 36 through its clockwise are into contact with arm 89 where, at the instant of contact, it is released without moving arm 89 and to drive arm 84 from adjustable stop 85 through its counterclockwise are into contact with arm 89 where, at the instant of contact, it is released without moving arm 89.

Solenoid 98 is connected to contactor 10. As aforestated, actuation of contactor 10 is controlled by the position of rod 12, rod 12 being positioned by the instantaneous magnitude of the variable being measured. Thus, during each rotation of transmitter cam 4, the time interval during which contactor 10 is closed and the time interval during which contactor 10 is open depends on the instantaneous magnitude of the variable. Since contactor 10 controls the energization and de-energization of solenoid 98 which, in turn, controls the relative arcs through which arms 74, 84, respectively, are rotated during each cycle of operation, the instantaneous magnitude of the variable being measured, as it varies rod 12 and contactor 10, is immediately reflected in the position of pointer 134 on scale 136.

While, in the foregoing description, motors 2 and 114 and solenoid 98 are connected to a single energy source, it is to be understood that separate sources may be provided. Since it is desirable that motors 2 and 114 rotate at a constant synchronous speed, it is preferred to connect the two motors in parallel to a common power source. However, solenoid 98 may be connected to a different power source in which event one of the solenoid leads would be connected directly to such source and the other lead would be connected to such source through contactor 10 and cam 4.

In the receiver of the instant invention a positive or gear-like drive is established and maintained between the stepped teeth 58, 60 of rings 58, 52 carried on driving plates 46, 4-8 and the stepped teeth 78, 88 of collars 76, 86 carried on driven arms 74, 84. As the stepped teeth of the driven arm are moved into engagement with the stepped teeth on the rings carried on the driving plates, the faces of stepped teeth extending at right angle and normal to the direction of drive are brought into contact. To prevent misalignment during operation, the U-shaped ends of arms 74, 84 are arranged so that only one leg of the U engages arm 89 with the point of contact between the U leg and the arm 89 substantially in the plane of the teeth on the corresponding ring. This arrangement prevents collars 76, 86 from cocking as might occur if the forces were non-coplanar. Thus, the vertical faces of the stepped teeth are maintained normal to the drive direction and a positive, locking drive is established between the two members until the teeth on the driven collar are with-drawn from the teeth on the driving ring by energizing or de-energizing solenoid 98. This positive drive is of substantial importance since it avoids any possibility of slippage.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. An indicator adapted to be controlled by impulses from a point remote from the indicator, said indicator comprising, a scale, a pointer movable across said scale, means for maintaining .said pointer positioned on said scale, a positioning member operatively connected to said pointer and movable between two predetermined points for positioning said pointer, a first arm for moving said positioning member from the first of said points toward the second of said points, a collar on said first arm, teeth on said collar, 2. second arm for moving said positioning member from the second of said points toward the first of said points, a collar on said second arm, teeth on said collar, a first toothed driving means adjacent said first arm for driving said first arm from the first of said points toward the second of said points, a second toothed driving means adjacent said second arm for driving said second arm from the second of said points toward the first of said points, a motor connected to said first and second driving means for driving said first and second driving means at a substantially constant speed in opposite directions, and means intermediate said first and second arms for alternately engaging and disengaging the teeth of the collar of said first arm with the teeth on said first toothed driving means and the teeth on the collar of said second arm with the teeth on said second toothed driving means, said first and second toothed driving means each containing, in the arc traveled by each of said toothed driving means during one complete cycle of engagement of said teeth on said first and second collars with the teeth on said first and second driving means, a whole number of teeth plus a pre-selected fraction of a tooth.

2 An indicator as recited in claim 1 in which said teeth on said collars and said teeth on said first and second driving means each have a surface for driving interengagement which is substantially normal in direction to the direction of drive of said first and second driving means and said collars.

3. In an indict-or adapted to be controlled by impulses from a point remote from the indicator having a scale, a

pointer movable on said scale and a positioning member operatively connected to said pointer and movable between two predetermined points, a drive for selectively moving said positioning member between said points, said drive comprising, a first arm for engaging said positioning member and for moving said member from the first of said points toward the sec-ond of said points, teeth on said first arm, a second arm for engaging said positioning memher and for moving said member from the second of said points toward the first of said points, teeth on said second arm, a first toothed driving means adjacent said first arm :for driving said first arm from the first of said points toward the sec-nd of said points, a second toothed driving means adjacent said second arm 'for driving said second am from the second of said points toward the first of said points, a motor connected to said first and second driving means for driving said first and second driving means at a substantially constant speed in opposite directions, and means intermediate said first and second arms for alternately engaging and disengaging the teeth on said first arm with the teeth on said first driving means and the teeth on said second arm with the teeth on said second driving means, said first and second toothed driving means each containing, in the arc traveled by each of said toothed driving means during one complete cycle of engagement of said teeth on said first and secondcollars with the teeth on said first and second driving means, a whole number of teeth plus a pre-selected fraction of a tooth.

4-. In an indicator as recited in claim 3 in which said teeth on said arms and said teeth on said driving means each have a surface for driving engagement which is sub- 8 stantially at right angle in direction to the direction of drive of said arms and said driving means.

5. An indicator adapted to be controlled by impulses from a point remote from the indicator, said indicator comprising, a scale, a pointer movable across said scale, means for maintaining said lpointer positioned on said scale, a positioning member operatively connected to said pointer and movable between two predetermined points for positioning said pointer, a first arm for moving said positioning member from the first of said points toward the second of said points, a collar on said first a-r-m, teeth on said collar, a second arm for moving said positioning member from the second of said points toward the first of said points, a collar on said sec-ond arm, teeth on said collar, a first toothed driving means adjacent said first arm for driving said first arm 'from the first of said points toward the second of said :points, a second toothed driving means adjacent said second arm for driving said second arm from the second of said points toward the first of said points, a motor connected to said first and second driving means for driving said first and sec-ond driving means at a substantially constant speed in opposite directions, and means intermediate said first and second arms for alternately engaging and disengaging the teeth on the collar of said first arm with the teeth on said first toothed driving means and the teeth on the collar of said second arm with the teeth on said second toothed driving means, said teeth being of such number on said first and second driving means, respectively, so that, during each complete cycle of alternate engagement of said teeth on said first and second driving means with the teeth of said first and second arms, said motor drives each of said first and second toothed driving means through an are, said are containing a whole number of teeth plus a preselected fraction of a tooth.

6. In an indicator adapted to be control-led by impulses from a point remote from the indicator having a scale, a pointer movable on said scale and a positioning member operatively connected to said pointer and movable between two predetermined :points, a drive for selectively moving siad positioning member between said points, said drive comprising, a first arm for engaging said positioning member and for moving said member from the first of said points toward the second of said points, teeth on said first arm, a second arm for engaging said positioning member and for moving said member from the second of said ]points toward the first of said points, teeth on said second arm, a first toothed driving -means adjacent said first a-rm tor driving said first arm from the first of said points toward the second of said points, a second toothed driving means adjacent said second arm for driving said second arm from the second of said points toward the first of said points, a motor connected to said first and second driving means for driving said first and second driving means at a substantially con- .stant speed in opposite directions, and means intermediate said first and second arms for alternately engaging and disengaging the teeth on said first arm with the teeth on said first driving means and the teeth on said second arm with the teeth on said second driving means, said teeth being of such number on said first and second driving means, respectively, so that, during each complete cycle of alternate engagement of said teeth on said first and second driving means with the teeth of said first and second arms, said motor drives each of said first and second toothed driving means through an are, said are contain ing a whole number of teeth plus a :pre-selected fraction of a tooth.

References Cited by the Examiner UNITED STATES PATENTS 2,976,740 3/1961 Frazel 74-319 DAVID J. WILLIAMOWSKY, Primary Examiner.

H. S. LAYTON, Assistant Examiner. 

1. AN INDICATOR ADAPTED TO BE CONTROLLED BY IMPULSES FROM A POINT REMOTE FROM THE INDICATOR, SAID INDICATOR COMPRISING, A SCALE, A POINTER MOVABLE ACROSS SAID SCALE, MEANS FOR MAINTAINING SAID POINTER POSITIONED ON SAID SCALE, A POSITIONING MEMBER OPERATIVELY CONNECTED TO SAID POINTER AND MOVABLE BETWEEN TWO PREDETERMINED POINTS FOR POSITIONING SAID POINTER, A FIRST ARM FOR MOVING SAID POSITIONING MEMBER FROM THE FIRST OF SAID POINTS TOWARD THE SECOND OF SAID POINTS, A COLLAR ON SAID FIRST ARM, TEETH ON SAID COLLAR, A SECOND ARM FOR MOVING SAID POSITIONING MEMBER FROM THE SECOND OF SAID POINTS TOWARD THE FIRST OF SAID POINTS, A COLLAR ON SAID SECOND ARM, TEETH ON SAID COLLAR, A FIRST TOOTHED DRIVING MEANS ADJACENT SAID FIRST ARM FOR DRIVING SAID FIRST ARM FROM THE FIRST OF SAID POINTS TOWARD THE SECOND OF SAID POINTS, A SECOND TOOTHED DRIVING MEANS ADJACENT SAID SECOND ARM FOR DRIVING SAID SECOND ARM FROM THE SECOND OF SAID POINTS TOWARD THE FIRST OF SAID POINTS, A MOTOR CONNECTED TO SAID FIRST AND SECOND DRIVING MEANS FOR DRIVING SAID FIRST AND SECOND DRIVING MEANS AT A SUBSTANTIALLY CONSTANT SPEED IN OPPOSITE DIRECTIONS, AND MEANS INTERMEDIATE SAID FIRST AND SECOND ARMS FOR ALTERNATELY ENGAGING AND DISENGAGING THE TEETH OF THE COLLAR OF SAID FIRST ARM WITH THE TEETH ON SAID FIRST TOOTHED DRIVING MEANS AND THE TEETH ON THE COLLAR OF SAID SECOND ARM WITH THE TEETH ON SAID SECOND TOOTHED DRIVING MEANS, SAID FIRST AND SECOND TOOTHED DRIVING MEANS EACH CONTAINING, IN THE ARC TRAVELED BY EACH OF SAID TOOTHED DRIVING MEANS DURING ONE COMPLETE CYCLE OF ENGAGEMENT OF SAID TEETH ON SAID FIRST AND SECOND COLLARS WITH THE TEETH ON SAID FIRST AND SECOND DRIVING MEANS, A WHOLE NUMBER OF TEETH PLUS A PRE-SELECTED FRACTION OF A TOOTH. 